SX Series Trimmer Cap

Over the years I've had to replace the trimmer capacitor most commonly designated as TC4 in many models of SX series receivers. They always use Pioneer p/n C43-007, C43-007-A, and ACM-006 which all sub to one another. This corrects a slow frequency drift problem. When first powered up, the tuning meter will be dead center but after a half hour, it will have drifted to the point of loosing the stereo reception. I know a lot of people have claimed to correct this problem by cleaning the grounds in the gang but my experience has been different for this particular problem. I have been harvesting known good TC's from non-drifting units and put them into the units that I would really rather have working. In almost all cases I can look at the bottom side of the defective tc and see tarnish on the plate that the wiper rests on. The working TC's have no tarnish. I am wondering if anyone else has seen this before and offer a clue as to this trimmers specification. So far I have found some that are very similar such as: hxxps://www.rfparts.com/capacitors/capacitors-certrimmer/capacitors-mini/3810-12.html Thanks for any clues.

I have the same drifting problem on AM with my SX-1980. After listening to AM, turning off the receiver and coming back to it later I have to move the dial slightly higher to be center tuned. Any idea what may be causing this?

I have no experience on the 1980 and the front end is not broken down the sm but if I had to guess, it would be TC0 which should be mounted right on top the the gang. Looks like the 1980 has an AFC component as well so as far as FM drift is concerned, another place to look would be the APC Board APX-124.Take that from some one who has never seen under the shield of a 1980 gang. I could never suggest to anyone who doesn't have experience on that tuner to attempt anything resembling repair....from what I've read, the 1980 can be a huge headache. No idea what would be causing your AM drift.

I have never measured the trimmers, but suggest that you do measure them using a good cap meter. Hopefully you have access to one. I would think that the trimmer be in the 2-10pF range. They can get expensive for good ones. Believe that the tarnish is silver oxide, probably a silver cleaner may work to clean up the old ones.

Cap meter shows 2.5-11pf which I knew all along but my main concern would be the other specs like temp in order to select a replacement. There are only so many donors. The cap in the link from the first post LOOKS identical to the original, but it's still a guess as to whether it would work. After 35 years of using this component, you'd think someone else out there would have done this already. Just looking for a proven result ya know?

Thanks for the RFParts link. I was looking for a source.

If your selection works (certainly do your own analysis before ordering-I posted a link to one that only looks like the original) please post part ID and results. Thanks.

Try this one
https://www.rfparts.com/3810-10.html
I do not think they used anything special or elabourate as far as temp compensation
Here is a selection to start with
http://ca.mouser.com/Passive-Compon...0wmvdZ1yzeeykZ1z0z819Z1z0z7xgZ1z0z7l5Z1z0z80h

I used the 3810-12 and it worked very well. A direct fit. Pre-set new one to 6.2 pF and it will be very close to original. Some cautions to observe; after taking off the original, let it cool down to room temp before testing. Let the gang chassis cool down before final adjustment of the new cap. This took about a half hour to cool.